How do add template on model space to existing template group and create a new sheet associated with the new template added?

I am currently trying to figure out how to add an additional viewport or template to the existing model space templates. Please correct my terminology if it's wrong. The first attachment shows my model space with 8 templates or viewports. The second image is the sheet space. I want to add another box to the eight existing boxes in the model space then have another sheet pop up corresponding to the new box added in the model space.